The present invention relates to plugging refractory materials having resin binder systems.
It is known that condensation products of formaldehyde with phenol or resorcinol can be used as binders in refractory materials. (U.S. Pat. No. 3,007,805, Column 3, lines 45-49.) Use of such conventional phenolic resin binders, however, has been characterized by high bonding strength in the low temperature range which may cause the material to solidify prematurely. (U.S. Pat. No. 4,072,531, Column 1, lines 25-30.) In plugging refractories, that is, refractories applied with a mud gun, this is very undesirable because it impairs the ability of the gunned refractory material to withstand residence periods in the mud gun without premature solidification.
Various solutions to this problem have been offered in the past. U.S. Pat. No. 4,022,739 implies that this problem may be overcome by adding to the resin a material which inhibits the speed of polymerization, e.g., hydroquinone or cobalt phthalate. (Column 2, lines 52-58). U.S. Pat. No. 4,072,531 suggests that this problem may be overcome by using a lignin-modified resin. (Column 1, lines 40-49.) U.S. Pat. No. 4,082,718 states that this problem can be overcome by adding to the resin an appropriate amount (0.5 to 10% of the resin) of the formaldehyde-source, cross-linking agent. (Column 5, lines 64-Column 6, line 14). Hexamethylenetetramine, acetal resin, paraformaldehyde, and trioxane are listed as suitable formaldehyde-source, cross-linking agents. (Column 6, lines 27-33.) None of these solutions, however, has been found to be altogether satisfactory.
The inventors have discovered that using tris (hydroxymethyl) nitromethane as the formaldehyde-source, cross-linking agent for a phenol-formaldehyde or resorcinol polymer resin binder system for a plugging refractory instead of a conventional formaldehyde-source, cross-linking agent for a phenol-formaldehyde or resorcinol polymer resin binder system for a plugging refractory, such as hexamethylene tetramine, increases the time it takes for the plugging refractory material to harden. On account of this longer hardening time, the plugging refractory material of the present invention can withstand longer residence periods in a mud gun without premature solidification.
In the past tris (hydroxymethyl) nitromethane has been primarily used as a bactericidal agent. It has also been used as a plasticizer in the preparation of phenol-formaldehyde resins to produce a more flexible, resilient resin. Heretofore, however, it has not been suggested that tris (hydroxymethyl) nitromethane can be used as the formaldehyde-source, cross-linking agent for a phenol-formaldehyde or resorcinol polymer resin binder system for a plugging refractory in order to increase the time it takes for the plugging refractory to harden, and thereby enhance the ability of the plugging refractory to withstand residence periods in a mud gun without premature solidification.